In the past, airless piston paint pumps had a cylinder and piston that typically required the use of tools to disassembly the cylinder from a drive assembly. One method of attachment of the cylinder was by way of interengaging screw threads on the cylinder and drive assembly. Often such cylinders had diametral flats to enable using a wrench to remove the cylinder from the drive housing.
Published patent application US 2006/0292016 A1 having the title RECIPROCATING PISTON PUMP SERVICEABLE WITHOUT TOOLS relates to an apparatus for removing the pump from the drive housing and describes using a hinged door having a latch assembly and a handle, with a safety latch to retain the handle in place during operation. Because the pump must be removed axially or longitudinally, the pump cylinder is supported only around half its circumference against forces acting on it when the piston is driven into the cylinder.